Alerted by the approaching shrill of a jet engine, Horst Kloster looked up to see the Ho-229 leave the confines of the military airfield and fly overhead. He smiled, picturing the series of events soon to unfold for the unsuspecting pilot: haziness, momentary confusion, difficulty in judgment, drowsiness, and if left unchecked, loss of consciousness.

Erwin Ziller was too preoccupied with the flight to notice the first subtle symptoms of hypoxia—fuzziness, drowsiness and lack of clarity. He followed up with another tight turn, a reciprocal turn, and then an abrupt drop in altitude, simulating a dog-fighting technique.

Afterward he felt disoriented but attributed it to the extreme manoeuver. That proved to be his undoing. A strange, hazy feeling hit him, followed by more confusion. He might have attributed this to lack of oxygen had it not been for an unexpected development; the right engine suddenly flamed out. Preoccupied with the sudden loss of power, Erwin didn’t realize that he was slowly succumbing to the effects of carbon monoxide poisoning. All his mental focus now hinged on trying to restart the starboard engine while maintaining control of the aircraft.

The drowsiness eventually affected him to the point that his thinking became scattered and confused. The first signs of panic hit his oxygen-starved brain, making him groggy. He was sliding toward a delirious state. He began to hallucinate, and the controller’s insistent calls, first a distraction, now became such a nuisance that he switched off the radio. More and more his thinking slowed, and in a final attempt at recovery, his hands fumbled with the latch, trying desperately to unhinge the canopy and escape the cockpit. Instead, he passed out.